NAME

dhcp - configuring OpenBSD for DHCP

DESCRIPTION

The Dynamic Host Configuration Protocol (DHCP) allows hosts on a TCP/IP
network to configure one or more network interfaces based on information
collected from a DHCP server in response to a DHCP request. This mechan-
ism is often used, for example, by cable modem and DSL network providers
to simplify network configurations for their clients/customers.
Information typically contained within a DHCP response includes an IP ad-
dress for the interface, subnet mask, broadcast address, router (gateway)
listing, domain name server listing, and the interface's MTU.
To set up OpenBSD as a DHCP client:
1. For each interface that is to be configured via DHCP, create a
/etc/hostname.XXX file (where XXX is the interface's identif-
ier, e.g., ep1) that starts with the word "dhcp", optionally
followed by additional interface options. See hostname.if(5)
for more information on the format of these files.
The /etc/netstart script reads each of these hostname files at
boot-time and runs the dhclient(8) program for each interface
that is to be configured via DHCP.
2. [Optional] To tweak settings, edit /etc/dhclient.conf. This
file is shipped with the system. See dhclient.conf(5) and
dhclient(8) for details.
To set up OpenBSD as a DHCP server:
1. Edit /etc/dhcpd.conf. This file is shipped with the system.
See dhcpd.conf(5) and dhcpd(8) for details.
2. Edit /etc/dhcpd.interfaces. This file should contain a list of
interfaces you wish to serve by dhcpd(8). If you have only one
broadcast network interface or you wish to serve all inter-
faces, this step is not required. Be sure to leave this file
empty (or even delete it) if this is the case.
3. Edit /etc/rc.conf.local and set dhcpd_flags="". This will
cause OpenBSD to start the dhcpd(8) daemon at boot-time and
listen for DHCP requests on the local network. To start it
manually, execute the following commands:
# touch /var/db/dhcpd.leases
# /usr/sbin/dhcpd -q [netif1 netif2 ...]
4. Ensure the kernel has been compiled with BPF (Berkeley Packet
Filter) support and at least one /dev/bpf* file exists per
broadcast network interface that is attached to the system.
This is almost always the case and should only be considered
if all other troubleshooting options have failed.
See dhcpd(8) for information on other available options. Note, however,
that most of the flags are useful only for debugging purposes.